Vapor etching of semiconductor materials and/or substrates is accomplished using gases, such as xenon difluoride. Specifically, in xenon difluoride etching, xenon difluoride gas reacts with solid materials, such as silicon and molybdenum, such that the materials are converted to a gas phase. The removal of these materials is known as etching.
Some of the gases used to perform vapor etching, such as xenon difluoride, can be expensive, hence, waste of this etching gas should be minimized. However, standard production etching systems in the semiconductor industry are typically not optimized to maximize gas utilization. In particular, Modular Equipment Standards Committee (MESC) compatible chambers, which are those which are typically connected in a cluster arrangement around a central robot, inherently have large chamber volumes. This large chamber volume is a result primarily of a side port used to provide access for the wafer. In addition, many MESC compatible chambers can be used for processing of large diameter wafers, e.g., 200 mm diameter wafer, but can also be used to process smaller diameter wafers, e.g., 100 mm diameter wafers. When using the larger chamber to process a smaller wafer, which is a common occurrence in facilities where more than one wafer size is used, further waste of etching gas occurs.
In addition, since MESC compatible chambers have a wafer loading port on one side, the chamber is inherently non-symmetric. Such asymmetry can lead to non-uniform etching of the wafer since the gas is not distributed axisymmetrically about the wafer.
What is, therefore, needed is a chamber such as, without limitation, an MESC compatible etching chamber or other etching chamber with a port on the side for loading, which has a subchamber assembly inside that creates a reduced chamber volume, is desirably axisymmetric shaped, that maximizes utilization of the etching gas and improves wafer etch uniformity.